Debutanization of naphtha



' July 28, 1936.

' J. R. SCHONBERG ET AL DEBUTANIZATION OF NAPHTHA Filed Nov. 10, 1930 Patented July 2a, 1936 UNITED STATES A r OFFICE DEBUTANIZATION OF N APHTHA ware Application November 10, 1930, Serial No. 494,587

2 Claims.

This invention relates to the removal of undesired low boiling components from hydrocarbon oil and more particularly to the debutanization of naphtha.

The invention will be fully understood from the following description taken in connection with the accompanying drawing, in which latter the figure is a diagrammatic showing of a preferred form of the invention.

Referring particularly to the drawing, reference numeral 1 designates a bubble tower which contains a plurality of plates having openings and bell caps associated with the plates at the openings. The bubble tower is connected with a cracking system by means of line 2 through which the products of the cracking reaction are adapted to be passed into an intermediate portion of the bubble tower wherein they are fractionated. Coolers 3 and 4 are provided in the bubble tower and a reboiler 5 is provided in the lower portion of the bubble tower. Feed stock for the cracking process is preferably used as the cooling medium in 3 and 4. Steam can be introduced into the lower portion of the bubble tower through line 6. Bottoms are withdrawn from the bubble tower through line 1 for recycling to the cracking reaction or for other utilization. The hydrocarbons in the tower are maintained under a pressure of approximately 120 lbs. per square inch and are withdrawn from the tower at a temperature of approximately 190 F. A naphtha and/or heavy naphtha side stream can be withdrawn from an intermediate portion of the bubble tower through a line 8 and passed through a steam stripper 9, where vapors consisting of steam and light ends are sepai'ated from the naphtha and are returned to the bubble tower through a valved line l0. As shown in the drawing, there is preferably no run-down from the plate supplying liquid to line 8; that is, the first stage fractionation in the lower part of tower l is conductedonly with reflux supplied by coil 3. Steam is introduced into the steam stripper through a line I I. The side stream from the bubble tower is the product of a second stage fractionation in the upper part of the tower and constitutes roughly half or the pentane formed in the cracking reaction and all of the heavier components boiling within the naphtha and/or heavy naphtha range. It will be understood that where butane, pentane, and other saturated hydrocarbons are referred to, their isomers and unsaturated hydrocarbons of the corresponding boiling range are also included. The bottoms from the stripper 5 withdrawn through a'line l2 constitute hydrocarbons substantially free from butane and lighter constituents. The bubble tower can be the single or the secondary bubble tower of a cracking system.

Overhead product containing roughly half of 5 the total pentane formed in the cracking reaction and all of the lighter components, together with similar components which are returned as reflux to the upper part of tower l is withdrawn from the towerthrough a line l3. This line com 10 municates with a condenser l4 in which the overhead is cooled to a temperature of approximately 115 F. and is discharged into a container IS. The steam and light ends from steam stripper 9 can be introduced directly into condenser 16 through a valved line l5 when desired. The condensate is passed through a line I 6 to a separator I! where' any water present is separated from the condensate. The separated condensate is passed by means of a pump l8 and line l9 into the upper portion of the bubble tower to function as reflux liquid.

Uncondensed vapors pass from container l5 through a line 20 and compressor 2| where they /are compressed to a pressure of approximately 25 250 lbs. per square inc The compressed vapors are cooled in a condenser 22 to a temperature of approximately F. whereby portions of the compressed vapors are condensed. The condensate is collected in a receptacle 23. The vapors are passed from receptacle 23 through a line 24 and compressor 25 where they are compressed to a pressure-of approximately 500 lbs. per square inch. The thus compressed vapors are cooled in a condenser 26 to a temperature of approximately 80 Fpwhereby a second condensate is formed which accumulates in receptacle 21. The gases or uncondensed vapors pass from receptacle 2'! through a line 28 to an absorption plant 29 where liquid constituents are derived fromthe gases. The residual gases are withdrawn from the absorption plant through a line 30 to a burning line, or other suitable place of disposal, not shown. Alternatively the vapors from the bubble tower can be compressed in one stage instead of in two stages to condense most of the heavier constituents and some of the advantages of the invention will be retained. I

The condensates contained in receptacles 23 and are conducted through. valved lines 32 50 and 33 respectively, into a bubble tower 35. Liquid derived from the absorption plant 29 can be returned to line 33 through a line .36. Line 33 opens into the bubble tower above the place of entrance of the condensate through line 32.

Bubble tower 35 contains a plurality of perforated plates and bell caps, not shown. The light naphtha bottoms in the bottom of bubble tower 35 are reboiled by means of heat derived from indirect heat exchange with the bottoms obtained from the steam stripper l0. These bottoms are introduced into the bubble tower through the line I! and are withdrawn therefrom through a line 39 to cooler 40. This debutanized naphtha can be treated, rerun and stored without appreciable evaporation losses. The light naphtha is rectified in bubble tower 35 under a pressure of approximately 190 lbs. per square inch and leaves the bubble tower at approximately 100 F. Reboiling of the naphtha in the lower portion of the tower is efiected by means of the auxiliary reboiler 4| into which the naphtha is introduced from the tower through a line 42 and is returned to the tower through a line 43. Vapors leave the tower through a line 44 and are cooled in a condenser 45 to a temperature of approximately 80 F. The resulting condensate is accumulated in a receptacle 46 and is returned to the upper portion of the tower through a line 41. Gases are discharged from receptacle 46 through a line 48.

The stabilized light naphtha bottoms are withdrawn from the bubble tower 35 through a line 50 and cooler and constitute a stabilized naphtha having an end boiling point of approximately 300 F. This stabilized light product can be refined, if necessary, and blended with the debutanized naphtha discharged through line 39 or can be blended with natural naphtha as desired.

While it has been described that reflux liquid for tower I has been provided from condenser l4, it will be understood that under certain conditions reflux liquid may not be returned from this point, but can be obtained from the condensate in receptacle 23 or can be obtained from the stabilized naphtha derived from cooler 5|.

By the process described, naphtha such as cracking coil gasoline is substantially freed o1 butanes with the recovery and stabilization of Various changes may be made within the scope oi. the appended claims, in which itis desired to claim all novelty inherent in the invention as broadly as the prior art permits.

We claim:

1. A process of separating naphtha from a mixture containing hydrocarbons boiling within the naphtha range, together with non-condensible gas, into debutanized and stabilized fractions comprising separating the naphtha by fractionation in a fractionating zone into a liquid heavy naphtha and a first vapor containing light naphtha hydrocarbons together with non-condensible gas, compressing the first vapor and cooling the same in a cooling zone maintained under high pressure to produce a condensed light naphtha fraction and a second vapor containing non-condensible gas, passing the second, vapor through an absorption system in which naphtha constituents are recovered and non-condensible gas is removed, and introducing the naphtha constituents recovered from the first vapor and the second vapor into a stabilizing zone in which further non-condensible gas is removed by rectification.

2. A process of separating naphtha from a mixture containing hydrocarbons boiling within the naphtha range, together, with non-condensible gas, into debutanized and stabilized fractions comprising separating the naphtha by fractionation in a fractionating zone into a liquid heavy naphtha and a first vapor containing light naphtha hydrocarbons together with non-condensible gas, cooling said first vapor to recover therefrom a liquid fraction, returning said liquid fraction to said fractionating zone as reflux, compressing the first vapor and cooling the same in a cooling zone maintained under high pressure to produce a condensed light naphtha fraction and a second'vapor containing non-condensible gas, passing the second vapor through an absorption system in which naphtha constituents are recovered and non-ccndensible gas is removed, and introducing the naphtha constituents recovered from the first vapor and the second vapor into a stabilizing zone in which further non-condensible gas is removed by rectification.

JACKSON R. SCHONBERG.

WILLARD E. ROBINSON. 

